Science & Technology

Exploring the Physics of White Dwarf Stars With Gravity Crystals [Video]

Hen’s eye view of a gravity crystal utilizing mm-sized aluminum spheres positioned on a conductive bowl-shaped floor. Excessive voltage from a Van de Graaff generator was utilized throughout the backside floor (graphite) and a clear conductive window positioned a number of centimeters above the balls. As soon as charged, the aluminum spheres repel each other, ultimately forming a periodic sample with each short- and long-range order. Credit score: Alexander Bataller

Seize a mixing bowl out of your kitchen, throw in a handful of aluminum balls, apply some excessive voltage, and watch a sublime dance unfold the place particles re-arrange themselves into a definite “crystal” sample. This curious habits belongs to the phenomenon often called Wigner crystallization, the place particles with the identical electrical cost repel each other to kind an ordered construction (high picture).

Wigner crystallization has been noticed in a spread of methods, starting from particulates the measurement of sand grains suspended in small clouds of electrons and ions (known as a dusty plasma) to the dense interiors of planet-sized stars, often called white dwarfs. Professor Alex Bataller of North Carolina State College has lately found that Wigner crystallization inside white dwarfs might be studied in the lab utilizing a brand new class of classical methods, known as gravity crystals.

Scientists research how charged particles prepare themselves into crystalline patterns and apply what they study to discover the interiors of white dwarf stars.

For the curious habits of Wigner crystallization to happen, there have to be a system composed of charged particles which might be each free to maneuver about (plasma), that strongly work together with one another (strongly coupled particles), and has the presence of a confining drive to maintain the plasma particles from repulsively exploding away from one another.

To review this situation for small scales in the laboratory, Dr. Bataller devised a brand new association that locations steel spheres involved with a excessive voltage confining floor, which expenses the spheres by transferring a whole lot of tens of millions of electrons to their floor, and thereby will increase particle repulsion, and in addition retains the particles contained. As well as, when the spheres roll over the floor, their movement produces friction that shortly reduces kinetic vitality and promotes sturdy coupling.

The important thing perception that enabled the current discovery was to make use of gravity as the confining drive. On this means, small charged spheres might be gravitationally confined utilizing a easy geometry…a bowl.

The pliability of the gravity crystal idea permits exploration of the identical physics that governs oxygen-carbon stratification inside cool white dwarf stars. This may be noticed by mixing completely different mass spheres (copper and aluminum) in “Alina’s bowl,” a shallow stainless-steel kitchen mixing bowl. As soon as voltage is utilized, the heavier copper balls “sink” to the bowl middle and separate from the lighter aluminum balls. Credit score: Alexander Bataller

By utilizing gravitational confinement, Dr. Bataller found that Wigner crystallization can be prolonged to macroscopic dimensions with particles 1,000,000 occasions extra huge than its dusty plasma cousin, which may now be used to check different crystal methods. For instance, gravity crystals can simulate a curious characteristic of white dwarf stars known as sedimentation. It was lately found that stratified crystal layers can kind inside white dwarf stars containing oxygen and carbon, the place the heavier oxygen “sinks” to the core. The gravity crystal association (second picture) reproduces this layering impact when making use of excessive voltage to an initially combined system of copper and aluminum balls. Analogous to sedimentation in white dwarf stars, the copper balls gravitate towards the bowl middle whereas sustaining a crystal construction.

The plasma properties and exterior surroundings of a gravity crystal and a white dwarf star are as completely different as one can think about, but each methods exhibit comparable habits, which speaks to the strong nature of Wigner crystallization.

“The wealthy variety of methods the place we’ve noticed Wigner crystallization is a direct outcome of its scale-independent nature,” Dr. Bataller mentioned. “Gravity crystals lengthen this phenomenon to human dimensions whereas needing minimal assets. What excites me most about this new platform is that nearly any curious particular person can recreate this fascinating state of matter that, till now, has been restricted to million-dollar experiments and inside the dense inside of stars.”


This research was supported by the Julian Schwinger Basis by grant JSF-18-09-0100.

For added data see additionally: P. E. Tremblay, G. Fontaine, N. P. G. Fusillo, B. H. Dunlap, B. T. Gänsicke, M. A. Hollands, J. Hermes, T. R. Marsh, E. Cukanovaite, and T. Cunningham, Nature 565, 202 (2019).


Gravity Crystals
2:00 PM-4:48 PM, Wednesday, October 23, 2019
Room: Grand G summary ID: PO11.00013

Alina’s Bowl: Demonstration of Macroscale Wigner Crystallization
2:00 PM-5:00 PM, Tuesday, October 22, 2019
Room: Exhibit Corridor A

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